I put up some new data, from a 10M-hand sample. (These files are pretty large, 236KB for the backs, 356KB for the middles, and 28KB for the fronts.)
http://www.lowballgurus.com/cp27/10M-backs-2.txt
http://www.lowballgurus.com/cp27/10M-middles-2.txt
http://www.lowballgurus.com/cp27/10M-fronts-2.txt
http://www.lowballgurus.com/cp27/10M-backs-3.txt
http://www.lowballgurus.com/cp27/10M-middles-3.txt
http://www.lowballgurus.com/cp27/10M-fronts-3.txt
I put up the distributions from two different iterations over the same set of hands, to illustrate how the maximally exploitive strategy switches strength between the front and the back/middle. There are about 2% fewer pairs in front in "3" than in "2".